Solving flow problems since 1894

ALDE ALDEN Research Laboratory, LLC Massachusetts | Colorado | Oregon | Washington

30 Shrewsbury Street, Holden, Massachusetts 01520-1843 508-829-6000 • www.aldenlab.com

Hydropower Feasibility Study

Norristown Dam Hydropower Consultation

RFP 21-64

Revision 00

Alden Job No. : ALD.0140001000

Prepared for:

Montgomery County Pennsylvania

May 2023

Norristown Dam Feasibility Study May 2023 ii

This Page Intentionally Left Blank iii

Name/Title Signature/Date Preparer (P)

Reviewer (R)

Benjamin Coleman

Engineer III

5/26/2023

P

Daniel Parker

5/26/2023

Jacob

Jenna

Kim

Steve Amaral

R

Gregory S. Allen, P.E.

Director, Environmental and

Engineering Services

5/30/2023

R

Record of Revisions

Revision

No.

Revision

Date Change Description Reason for Change

0 05/30/2023 Initial Issue iv v

Table of Contents

Executive Summary ................................................................................................................................. xiii

1.0 Introduction

1.1 Background

1.2 Project Description

1.3 Review of Previous Work

1.3.1 2017 Resource Assessment

1.3.2 2017 Feasibility Study

1.3.3 Preliminary Permit

1.3.4 Licensing Alternatives Analysis

1.3.5 Initial Consultation Document

2.0 Objectives and Approach

3.0 Hydropower Development and Site Technical Evaluation

3.1 General Characteristics and Methodology of Hydropower Production

3.2 Head

3.2.1 Headwater Elevation

3.2.2 Tailwater Elevation

3.2.3 Gross Head

3.2.4 Head Loss

3.2.5 Net Head

3.3 Flow

3.3.1 Schuylkill River Flow

3.3.2 Non-power Flow Requirements

4.0 Review of New Technology

4.1 AMJet ATS Turbine

4.2 Natel Energy Restoration Hydro Turbine (RHT)

4.3 KW River

4.4 VLH (Very Low Head) Turbine

4.5 Littoral Power Systems FlexStream

5.0 Request For Quotation of Turbine-Generator Equipment

6.0 Norristown Dam Development Analysis

6.1 Influence of Previous Study

6.2 Design Assumptions and Criteria

6.3 Alternative 1 – Seven Voith Units

6.3.1 Design

6.3.2 Construction

6.3.3 Advantages and Disadvantages

vi

6.4 Alternative 2 – Seven Mavel Units

6.4.1 Design

6.4.2 Construction

6.4.3 Advantages and Disadvantages

7.0 Energy Modeling

7.1 Head

7.2 Generating Flow

7.3 Efficiency

7.4 Energy Model

8.0 Economic Evaluation

8.1 Asset Value Estimate Investigation

8.2 Costs

8.2.1 Equipment Costs

8.2.2 Development Cost Opinions

8.2.3 Permitting and Engineering

8.2.4 Operation and Maintenance Cost Estimates

8.3 Value of Energy Investigation

8.3.1 Power Sales Revenue

8.3.2 Renewable Energy Credits/Alternative Energy Credits

8.3.3 Ancillary Services

8.3.4 Montgomery County Electric Use

8.4 Review of Grants, Financing, and Incentives

8.4.1 Inflation Reduction Act (IRA) of 2022

8.4.2 Infrastructure Investment and Jobs Act (IIJA) of 2021

8.4.3 Microgrid

8.4.4 Alternative Energy Credits (RECs)

8.5 Estimated Payback Period and return on Investment

9.0 Examples of Municipal Hydropower

10.0 Summary

10.1 Conclusions

10.2 Next Steps

10.2.1 Pursue funding

10.2.2 Optimization

10.2.3 Sell the Asset

10.2.4 Dam Removal

10.2.5 No Action

11.0 References

vii

Appendix A – Environmental Impacts Memorandum

Appendix B – Socioeconomic Impacts Memorandum

Appendix C – Select Reference Drawings

Appendix D – Monthly Flow Duration Curves

Appendix E – Turbine Vendor Information

Appendix F – Conceptual Design Drawings

Appendix G – Cost Opinion Report viii

List of Tables

Table 3-1. Summary of rough field head measurements

Table 3-2: Summary of flood flows

Table 5-1: List of vendors contacted

Table 5-2: Information provided by suppliers for each design

Table 6-1: Summary of existing elevations used in design

Table 6-2: Summary of proposed Voith Unit characteristics

Table 6-3: Summary of proposed Mavel unit characteristics

Table 7-1: Environmental and aesthetic flows

Table 7-2: Modeled site flow rates

Table 7-3: Estimated efficiency used in modeling

Table 7-4: Mavel power modeling results

Table 7-5: Estimated annual energy production

Table 8-1: Regionally adjusted wage rates

Table 8-2: Alternative 1 - Seven Voith Units quantity takeoffs

Table 8-3: Alternative 2 - Seven Mavel Units quantity takeoffs

Table 8-4: Development cost range

Table 8-5: Summary of costs used in proforma modeling

Table 8-6: Summary of estimated O&M costs

Table 8-7: Projected energy and cost savings for the Courthouse and One Montgomery Plaza 69

Table 8-8: Summary of available incentives review

Table 8-9: Proforma for net metering scenario and current financing case

Table 8-10: 20-year breakeven financing with grants

Table 8-11: 20-year breakeven financing with increased energy value

Table 9-1: New or reconstructed municipal hydropower projects

Table 10-1: Summary of proforma out puts

Table 10-2: Summary of cost increase from the 2017 study

List of Figures

Figure 1-1: Norristown Dam location map

Figure 1-2: Norristown Dam area map

Figure 1-3: Norristown general layout

Figure 1-4: Plan view of Denil fish ladder

Figure 3-1: Hydraulic turbine type efficiency comparison (ESRU 2017)

Figure 3-2: Hydraulic turbine application chart (Maskauskas 2007)

Figure 3-3: Typical layout of a Kaplan turbine (Voith-Siemens 2005) ix

Figure 3-4: Ossberger crossflow turbine (ossberger.de)

Figure 3-5: Overview of net and gross head through a hydropower system

Figure 3-6: USGS Gage 01473500 location (USGS 2017)

Figure 3-7: Headwater elevation derivation

Figure 3-8: Tailwater elevation derivation

Figure 3-9: Gross head based on tape measurements taken in 2016

Figure 3-10: Head and tailwater curves from the “Contract Drawings for Construction of Fish

Passage Facilities at Norristown Dam - Sheet G9 Fishway Schematic” Gannett Fleming. Inc 2008.

Figure 3-11: Norristown Dam drainage area (area in yellow) (StreamStats 2017)

Figure 3-12: Average monthly flowrate

Figure 3-13: Yearly minimum, average, and maximum flow

Figure 3-14: Norristown dam flow duration curve

Figure 4-1: AMJet ATS turbine (amjethydro.com)

Figure 4-2: Natel RTK (natelenergy.com)

Figure 4-3: Schematic of Williams crossflow turbine (kwriver.com)

Figure 4-4: VLH turbine (vlh-turbine.com)

Figure 4-5: Littoral Power FlexStream turbine (littoralpower.com)

Figure 6-1: Alternative 1 general layout

Figure 6-2: Alternative 1 plan view

Figure 6-3: Alternative 1 plan view catwalk details

Figure 6-4: Alternative 1 elevation view

Figure 6-5: Alternative 2 general layout

Figure 6-6: Alternative 2 plan view with catwalk detail

Figure 6-7: Alternative 2 concrete roof plan view

Figure 6-8: Alternative 2 main work floor plan view

Figure 6-9: Alternative 2 elevation view

Figure 6-10: Alternative 2 detailed elevation view

Figure 6-11: Alternative 2 gate elevation view

Figure 7-1: Gross head as a function of river flow

Figure 7-2: Flow duration chart for Voith Turbines

Figure 7-3: Flow duration curve for Mavel Turbines

Figure 8-1: Average daily wholesale energy prices in PJM 2015 to 2021 x xi

TRANSMITTAL LETTER

May 30, 2023

Drew Shaw

Environmental Planning Manager

Montgomery County Planning Commission

P: 610.278.3733 F: 610.278.3941

PO Box 311, Norristown, PA 19404-0311

425 Swede St., Suite 201, Norristown, PA 19401

Draft Feasibility Study Report for the

Norristown Dam

Dear Mr. Shaw, As described in Alden Research Laboratory, LLC’s Proposal No. : ENV-21-P-158 submitted March

25, 2022, I am pleased to submit this draft Hydropower Feasibility Study Report for your review.

The RFP 21-64 scope of work also included a FERC Licensing Alternatives Analysis and the development of an initial FERC submittal document; these were submitted to the County separately.

Please do not hesitate to contact me with any questions or comments.

Sincerely, Benjamin Coleman xii xiii

Executive Summary

Interest in developing the hydropower potential at the Norristown Dan was generated following the U.S. Department of Energy’s Oak Ridge National Laboratory study, An Assessment of Energy

Potential at Non-Powered Dams in the United States, identifying the dam as one of the many existing non-powered dams in the United States with energy producing potential. Alden investigated the Dam’s hydropower potential in greater detail, which was presented in a 2017 feasibility study, for Montgomery County. Although the results of the 2017 study indicated that the project did not appear to be economically viable, due to recently announced funding opportunities and potential improvements through refining the conceptual designs, the County has decided to explore the viability of the project in today’s market.

This study assesses the current value of the dam, updates river flow and head values, investigates turbine equipment applicability and performance, revises conceptual designs, updates financing and economic modeling, reviews potential environmental and socio-economic impacts, and presents examples of other municipally owned hydroelectric projects.

Several property and equipment assessors were solicited to estimate the current value of the property and how this might change at various stages in development. The general consensus was that the property has little to no value in its current state and the future potential value would be assessed as an operating hydropower plant, or any other business, based on revenue generating potential or comparable sales if they exist. The project’s revenue generating potential was analyzed as part of this study and the approach and results are included in this report.

To update hydropower technology and pricing information, a technology review was conducted, and quotes were solicited from several vendors who have equipment which was conducive to the Norristown Dam site. Fifteen vendors were contacted and six provided budgetary costs and designs. Of those, two vendors, Voith and Mavel, were determined to have the most technically and financially viable proposals. These were used in conceptual designs.

Two primary design alternatives were developed; a concept using Voith StreamDivers similar to those used in the 2017 study, and a concept using updated Mavel Kaplan units. Both concepts were analyzed with seven-, six-, and four-unit alternatives. The resulting six alternatives include,

• Alternative 1 – Seven Voith Units

• Alternative 2 – Seven Mavel Units

• Alternative 3 – Six Voith Units

• Alternative 4 – Six Mavel Units

• Alternative 5 – Four Voith Units

• Alternative 6 – Four Mavel Units

These concepts were intended to further develop the matrix-style design that was determined to be the most feasible in the 2017 study. As such, all six designs are matrix-style structures placed on the right bank adjacent to the fish ladder. The most significant differences in the designs involve the structure in which each type of unit is installed and the need to compensate for lost flood flow passage capability. The Voith units have submersible turbine-generators and do not require a powerhouse or dry operating area, whereas the Mavel units are more traditional

Kaplan turbines with a submerged turbine runner connected through a gearbox to a generator located in a dry operating area. As the Mavel designs require a powerhouse which reduces the capacity of the existing dam to pass flood flows, additional gates are required to maintain that capability. It is important to note that any changes in spillway capacity will be subject to a no-xiv rise analysis for which it must be proven that the proposed project will not affect the 100-year floodplain. The gates included in the Mavel designs are conceptual in nature, having been designed with a high-level numeric model. Detailed design of the Mavel concepts will require comprehensive modeling of the project which may have significant impact on the gate size and design, and ultimately the feasibility of these alternatives. Other differences between the

Voith and Mavel concepts include operational versatility, and cost. The Voith units have a narrow operating range where the startup flow is about 90% of the nameplate capacity; thus the Voith units essentially operate in the on or off position. The Mavel units have adjustable wicket gates and runner blades. This allows the unit to start up at the much lower turbine flow, 40% to 50% of name plate capacity, and remain efficient over a broader range of flows. The

Mavel quote for their equipment was also about 43% less expensive than the Voith.

Alden and On Point Construction Services (On Point) developed construction cost opinions for the two primary alternatives. These cost opinions were adjusted to apply to the remaining four alternatives. Although the Voith equipment was more expensive, the requirement for the dry operating area for the Mavel units resulted in an overall higher cost for the Mavel designs. The total cost opinion for the four alternatives was,

• Alternative 1 – Seven Voith Units $28,800,000

• Alternative 2 – Seven Mavel Units $32,400,000

• Alternative 3 – Six Voith Units $26,100,000

• Alternative 4 – Six Mavel Units $29,300,000

• Alternative 5 – Four Voith Units $20,600,000

• Alternative 6 – Four Mavel Units $23,100,000

The Mavel cost opinions are about 11% higher than the comparable Voith opinions. However, total development costs per kW installed ($/kW) were 31% to 54% higher than the most viable alternative evaluated in 2017. The increase is attributable to both higher construction costs and lower energy pricing.

In the 2017 study, the value of energy used in modeling was based on the retail price the

County was paying; at that time, this price was $0.086 per kWhr. The County has since entered into a power purchase agreement (starting in 2024) with an initial rate of about $0.067 per kWhr.

This is about a 22% decrease in cost, or equivalent decrease in the value of energy for the project. While this reduction in the price that the County will pay for electric energy is beneficial to the County, it reduces the future revenue value of the hydroelectric development. The updated development cost opinions, revenue data, and regulatory process costs were incorporated into a new economic performance (proforma) model.

Using the assumed inputs as described in this report, proforma modeling estimated Alternative 5

– Four Voith Units would result in a 20-year net average annual income of about $47,000. All the other alternatives were estimated to have a negative return for the first 20 years. Once the loans are paid off, following the 20-year mark, all six alternatives were estimated to have a positive net annual income.

To provide an estimate of what would be required to make the project more economically viable, additional modeling was performed to determine the level of funding that would result in the project breaking even in 20 years (20-year NPV equal to zero). In a second variation, the model was adjusted to determine the value of generated energy that would be required for a

20-year NPV of zero. These additional proforma estimate that the project would require 81% to

85% external funding, or a value of energy of increase of about 360% to 420% to make the project break even in 20 years at a 6% discount rate. In the break-even scenario using grant xv funding the most viable option would be Alternative 1 – Seven Voith Units, with an average 20-year net annual income of about $483,000.

Alden also investigated other options that the County may consider if developing hydropower at the Norristown Dam is not implemented. Those options include pursuing additional funding from external sources, seeking a buyer or partner to acquire the dam and develop hydropower under a different financial construct, removing the dam, or no action.

xvi

1.0 Introduction

1.1 Background

The Norristown Dam (Norristown) is owned by Montgomery County, PA (County) and is located approximately 15 miles northwest of Philadelphia Pennsylvania, spanning the Schuylkill River between

Norristown and Bridgeport Pennsylvania, as seen in Figure 1-1 and Figure 1-2. The Norristown Dam was identified by the United States Department of Energy’s Oak Ridge National Laboratory as an existing unpowered dam with small hydropower potential (Hadjerioua, 2012). In 2016, Alden Research

Laboratory, LLC (Alden) was contracted by the County to conduct a site visit and a two-phase

Feasibility Analysis of the Norristown Dam to assess the site’s generating potential. No insurmountable barriers to hydropower development at the site were identified in the Resource Assessment. As a result, the County authorized Alden to move forward with the Phase 2 Feasibility Study. In December of 2017, Alden submitted the “Norristown Dam Feasibility Study” to the County. The County did not move forward with developing the site at that time.

With recent changes in the Federal Energy Regulatory Commission (FERC) licensing regulations, new commercially available hydropower generating technology, and the federal funding for green energy development projects included in the Infrastructure Investment and Jobs Act and the Inflation

Reduction Act, there is potential to improve the financial viability of and renewed interest in hydropower development at Norristown.

In April of 2021, Alden responded to the County’s Request for Information (RFI) and provided the following recommendations,

1. Submit application to the Federal Energy Regulatory Commission for a preliminary permit/

Exemption under FERC’s new 10MW exemption rules. This will protect the County’s interest in developing the project by ensuring that the County is “first in line” to be granted the authority to pursue developing the site.

2. Explore opportunities to partner with a developer to develop the project. Alden can assist the

County in identifying hydropower developers and initiating those discussions. Alden staff are actively engaged with several hydropower developers.

In November of 2021, the County released the Request for Proposal (RFP 21-64) Hydroelectric

Conversion Consulting Services at the Norristown Dam, in which the County requested a FERC authorization alternatives analysis, drafting of FERC documentation, and an updated feasibility study.

Alden was awarded the contract and the following report is the Feasibility Study portion of the project.

Figure 1-1: Norristown Dam location map

Figure 1-2: Norristown Dam area map

1.2 Project Description

The existing Norristown Dam consists of an 869 foot long 12-foot-high concrete capped timber-crib dam, set in a wide V shape approximately north to south across the Schuylkill River. The dam terminates at a stone-block abutment on the north (Norristown) end and to a fish ladder structure on the south

(Bridgeport) end (Figure 1-3). The Denil fish ladder is set along the southern bank of the river with an entrance at the downstream dam apron, set at about a 20-degree angle to the river bank and an exit upstream of the dam, about 90 degrees to the embankment (Figure 1-4). At about the mid-point of the fish ladder structure is an intake for attraction flow for the fish ladder. Water drawn in at this point is piped to a diffuser at the entrance of the ladder; the additional flow is intended to help migrating fish locate the entrance. The fishway operates seasonally from mid-April through the end of October and is designed to pass 25,000 American shad per year. A SEPTA light rail bridge and the U.S. Route 202 vehicle and pedestrian bridge also span the river, about 100 ft and 600 ft downstream of the dam, respectively.

Figure 1-3: Norristown general layout

Figure 1-4: Plan view of Denil fish ladder

1.3 Review of Previous Work

1.3.1 2017 Resource Assessment

The 2017 Norristown Dam Resource Assessment included a brief history of the dam, a summary of existing conditions and environmental resources that may impact development, a preliminary analysis of the power generating potential available at the site, power and energy production estimates, conceptual development options, and preliminary financial evaluations. The assessment included a review of the following:

• Existing conditions and environmental resources, o Water resources, o Water quality, o Geology and soils, o Fish and aquatic resources, o Fish passage, o Wildlife and botanical resources, o Wetlands, floodplains, riparian, and littoral resources, o Rare, threatened, and endangered species, o Recreation and land use, o Cultural and historic resources,

• Generation resources, o River flows.

o Available generation flows, o Head, o Efficiency,

• Power and energy estimates,

• Development options,

• Financial evaluation, o Preliminary conceptual cost estimate, o Value of energy, o Operations, maintenance, and other costs, o Financing, and o Estimated payback period and return.

The Resource Assessment did not identify any potential fatal flaws at or associated with the site that would prevent hydropower development. However, the potential benefits would be dependent on the ability to use the power to offset retail costs, wholesale energy prices, and other potential incentives.

1.3.2 2017 Feasibility Study.

The Feasibility Study provided a more in-depth review of many of the same elements in the Resources

Assessment along with conceptual designs and a more detailed economic evaluation. Alden developed five conceptual hydropower design options including two options on the shore side of the existing fish ladder and three options on the river side of the fish ladder. The two shore side options were determined infeasible, largely due to the close proximity of a bridge pier and utility tower just downstream of the site. Following an initial screening, the three river side options were selected for economic evaluation. The economic evaluation included the following:

• Detailed flow evaluation,

• Detailed head estimate,

• Procurement of turbine quotations,

• Development of conceptual layouts,

• Daily power and energy modeling,

• Cost estimates,

• Energy value investigation,

• Detailed resource investigation,

• Review of grants and other incentives such as renewable energy certificates (RECs), and

• Detailed proforma.

The proforma was completed for each of the three selected options under three separate financing scenarios. Given the available hydropower generating technology and financing options in 2017, the development was considered to be technically feasible but only financially viable under limited scenarios.

1.3.3 Preliminary Permit

In 2020, the County contracted Alden to develop a Federal Energy Regulatory Commission (FERC) preliminary permit application and necessary attachments for the Norristown site. A preliminary permit is issued for up to four years and maintains the priority of application for license while studies for the site are completed and the license application is prepared. Due to changes in FERC licensure rules, it became unclear if applying for the preliminary permit was in the County’s best interest at the time, and the application was not submitted to FERC.

1.3.4 Licensing Alternatives Analysis

In 2022, Alden prepared a FERC licensing alternatives analysis report to inform the County and other stakeholders regarding FERC’s approval process and how it would apply to hydropower development of the Norristown Dam site.

The report introduced FERC processes, how they regulate hydropower development and operations, and the various routes that may be taken to obtain FERC approval, which include the following regulatory processes:

• Preliminary permit,

• Exemption,

• Licensing,

• Integrated Licensing Process (ILP),

• Traditional Licensing Process (TLP), and

• Alternative Licensing Process (ALP)

The report included details that should be considered when making the decision to seek FERC approval and which route to choose. These considerations include other required permits and approvals outside of FERC, potential study commitments, estimated expenses, and estimated time commitments. The most influential of these are the costs and time commitments. As these are difficult to estimate accurately at this stage of development, high and low estimates were developed to provide a range for each. The estimated cost for FERC licensing for hydropower development at the Norristown Dam ranged from about $460,000 to $830,000, and the time commitment was estimated at approximately 3.5 to four years.

Based on the information provided in the report, should the County decide to seek FERC approval for hydropower development at the Norristown Dam, Alden recommended applying for an exemption as opposed to a license. An exemption application requires a lower level of effort than that of the license and, if approved, the exemption goes on into perpetuity, unlike the license, which must be periodically renewed. Thus, the exemption would be preferable to a license and a more valuable asset for the project. An exemption would be granted on a case-by-case basis. It is unclear if FERC will approve an exemption for this site; however, there is enough evidence in the regulations to suggest the site will qualify for an exemption, to justify seeking this route of FERC approval. Should the exemption application be denied, the County may pursue a licensure path and maintain their priority position with

FERC.

1.3.5 Initial Consultation Document

Alden and the County have drafted an Initial Consultation Document (ICD) that will begin the process of applying for a FERC exemption for the Norristown Dam Project.

The ICD includes a description of the existing environmental resources and potential impacts the project may have on those resources, a proposed hydropower project description, operations plan, and a construction plan and schedule. According to 18 CFR § 4.38, stakeholders, resource agencies, and members of the public will have an opportunity to be educated about the proposed project as well as comment on the ICD before preparation and submittal of the exemption application. The

County will hold a joint agency and public meeting on a date between 30 and 60 days after the submittal of the ICD to FERC. A notice of a public meeting will be published in a local paper two weeks prior to the joint meeting. A site visit will also be scheduled for the same day as the public meeting.

Throughout the exemption process, a written record of the documents, meetings, and discussions will be maintained in the FERC e-library, as well as in a local repository for public and other stakeholder access.

As of the date of this report the ICD has not been submitted to FERC.

2.0 Objectives and Approach

The objective of this study is to provide the County with the information needed to make informed decisions regarding hydropower development at the Norristown Dam. This was accomplished by providing a review of previous research completed for this site, evaluating the resources (such as head and flow) available at the site, reviewing new technology since the 2017 study, requesting new information from hydropower equipment suppliers, creating and refining conceptual designs based on the new vendor information, and performing an economic analysis for the conceptual designs

(including up-to-date funding and value of energy research. Examples of other municipality-owned and developed hydroelectric projects have also been included to assist the County with its deliberations.

Information regarding the potential environmental and socioeconomic impacts of the development may be found in Appendix A – Environmental Impacts Memorandum and Appendix B – Socioeconomic

Impacts Memorandum.

3.0 Hydropower Development and Site Technical Evaluation

Hydropower generation potential is a function of head, flow available for generation, and system efficiency. This section presents an overview of applicable hydropower technology and available head and flow resources at the Norristown Dam site.

3.1 General Characteristics and Methodology of Hydropower Production

Hydro-turbines convert the available water pressure into mechanical shaft power, which drives an electrical generator. A turbine converts the potential energy from falling water into kinetic rotational shaft power. The power available from a hydroelectric system is a function of the available net head, the flow rate through the turbine, and the overall efficiency of the hydroelectric generating system. The efficiency of a system is highly dependent upon the type of turbine. Different turbine technologies are best suited to particular head and flow combinations. Some turbines can have hydraulic efficiencies in the range of 90 percent. Also, some turbines maintain a higher efficiency at a water flow rate less than that of design maximum power output. This is important as the available flow at most sites fluctuates and cannot continuously support full power operations. A unit with a higher efficiency over a wider range of likely flows will make more power during lower than ideal flow conditions. Figure 3-1 shows that a Francis turbine is significantly less efficient at lower power settings than a full Kaplan turbine and the propeller turbine is highly efficient at a singular design point, but rapidly decreases over the remaining operating range.

Figure 3-1: Hydraulic turbine type efficiency comparison (ESRU 2017)

The selection of the best turbine for a site is dependent upon the site characteristics, particularly the available head and flow. Other considerations such as the anticipated range of flows expected throughout a typical year and the efficiency of turbines over those ranges of flows are also important.

The turbine application chart shown below provides a graphical overview of turbine type operating ranges (Figure 3-2).

Figure 3-2: Hydraulic turbine application chart (Maskauskas 2007)

There are two broad categories of turbines; impulse and reaction turbines. Impulse turbines use the velocity of a jet of water to move a turbine runner and produce power, these include Pelton, turgo, and crossflow (also known as a banki turbine). Any turbine where the water velocity accelerates relative to the runner is a reaction turbine. Typical reaction turbines include Francis, Kaplan, and propellers. As shown in Figure 3-2, impulse turbines typically operate under higher head / lower flow conditions while reaction turbines typically operate under lower head / higher flow conditions, with the exception of the crossflow. Also shown in Figure 3-2, is the anticipated operating range at the Norristown site, illustrating that Kaplan (including non-regulated Kaplan or, propellor) and crossflow turbines would be best suited for the project.

A Kaplan turbine is shown in Figure 3-3. The Kaplan turbine runner looks like a ship’s propeller, but the pitch of the blades is adjustable to optimize generation with available head and flow. A full Kaplan turbine, or double-regulated, also includes adjustable guide vanes called wicket gates that control the volume and angle of the flow approaching the runner. A semi-Kaplan turbine, or single regulated, has adjustable pitch blades but has a fixed inlet guides. A propellor runner is similar to a Kaplan but with fixed blades and fixed guide vanes. A double regulated (full) Kaplan turbine is the preferred unit in many installations due to its high versatility and efficiency over a range of operating conditions. The additional regulating capacity comes at a higher cost than a single-regulated turbine or a propellor turbine.

Figure 3-3: Typical layout of a Kaplan turbine (Voith-Siemens 2005)

A crossflow turbine creates a horizontal jet of water that impacts a horizontal waterwheel-type runner, the rotating runner shaft then rotates a generator, see Figure 3-4. The advantage of this design is that in low flow conditions the portion of the waterwheel in use may be reduced, however, the crossflow turbine is typically less efficient than reaction type and other impulse type runners.

Figure 3-4: Ossberger crossflow turbine (ossberger.de)

3.2 Head

The gross head available for power generation is the difference in elevation between the upstream and downstream water surface elevations. Net head is broadly defined as the gross head minus the hydraulic losses throughout the system. The available head is both a function of the volumetric flow and hydraulic characteristics of the upstream and downstream channels as shown in Figure 3-5.

Figure 3-5: Overview of net and gross head through a hydropower system

Available head for Norristown was estimated with the use of polynomial fit equations for available data sources including field data collected at the site, historical United States Geologic Service (USGS)

Stream Gauge (#01473500) water surface elevation data and published Federal Emergency

Management Agency (FEMA) flood plain information.

Preliminary gross head measurements were taken by Alden during a site visit and later by the County.

Head across the dam was estimated by measuring with a steel tape down from the fish ladder platform

(right dam abutment) to the water’s surface upstream and downstream of the dam. Table 3-1 provides a summary of these measurements. The gross head across the dam was estimated as the distance from the deck to the tailwater minus the distance from the deck to the headwater. Due to some inconsistencies not all measured head data were used in the evaluation.

Elevation benchmarks from previous project construction drawings were then applied to the field data.

An abutment elevation of 63.1 ft NGDV1 (Site Plan G1 8/19/1993) and a dam crest elevation 58.3 ft

NGDV (Section and Details S-2 8/19/1993) were used for basepoints. A head measurement taken by

Alden during the site visit was used along with USGS gage data to calculate a discharge coefficient for weir flow over the spillway to verify other survey data. The weir equation is shown in Equation 3-1 below, Equation 3-1: Weir equation

Q = 𝐶𝑑 ∗ L ∗ 𝐻(

Where:

Q = Flow in cubic feet per second (cfs)

1 Drawings indicated NAVD datum but did not specify NAVD29 or NAVD88

Cd= Discharge coefficient

L = Length Weir (ft)

H = Flow depth over weir (ft)

A discharge coefficient of 2.81 was calculated utilizing the drawing benchmarks and Alden survey data for a 15-minute USGS gauge flow of 527 cfs reported at the time of the survey. This checked well against standard literature for broad crested weirs with a range from approximately 2.75 through 2.90 for similar flow depth versus weir width (Tracy 1957). A depth for each of the County surveyed points was calculated using the USGS gauge flowrate and then compared to the measured values. Due to datum inconsistencies, some measured head values were not used to determine actual headwater and tailwater surface elevations but were used to determine the total elevation differential between headwater and tailwater.

It is important to understand the portion of the available head from the depth of water over the spillway crest. When the head measurements were conducted all project inflow was routed over the crest of the dam. Once the project is operational, a certain portion of the project inflow will be discharged through the turbines and will not be discharged over the weir crest. Since the turbine flow rate is not discharged over the crest it does not lead to a deeper flow over the crest and a subsequently higher headwater elevation. If the measured head values are utilized directly to calculate the headwater elevation the head will likely be overestimated. If the headwater surface elevation versus flow rate can be identified, the measured differential head values can be used to find the corresponding tailwater elevation.

Table 3-1. Summary of rough field head measurements

Survey

Source Date Time

USGS

Flow Rate

(cfs)

Deck to

Above

Dam

(ft)

Deck to

Below

Dam

(ft)

Measured

Head

Differential

(ft)

Alden 11/18/2016 12:00 527 4.42 13.7 9.3

County 2/6/2017 11:00 1,250 4.75 13.6 8.8

County 2/23/2017 13:30 1,330 4.63 13.6 9.0

County 8/3/2017 14:00 2,340 4.38 13.2 8.8

County 4/5/2017 10:00 7,030 4.08 11.8 7.7

3.2.1 Headwater Elevation

USGS Gauge 01473500 (USGS Gauge) was identified as a source of data for flowrate and headwater elevation. The USGS Gauge is located on the Schuylkill River at the Haws Avenue Bridge , 0.2 miles upstream from the confluence of Stony Creek and 0.6 miles upstream from Norristown Dam at 40°06'40", 75°20'50". The gauge relies upon the water surface elevation of the impoundment to calculate a flowrate for the Schuylkill River. The water surface elevation of the impoundment is directly related to the depth of water over the spillway crest. This means that there is a recorded source of available flowrate versus headwater elevation data for the project. A picture of the USGS Gauge location adjacent to the Barbadoes Island Bridge can be seen in Figure 3-6.

Figure 3-6: USGS Gage 01473500 location (USGS 2017)

Approximately 6 months of fifteen-minute flow and water surface elevation data from April to October

2017 was taken from the USGS gage. This data spanned a river flow from approximately 700 cfs to

18,000 cfs. The data was fitted using a third order polynomial equation for spillway flowrates from 1,000 to 18,000 cfs. For flows less than 1000 cfs, a second polynomial curve fit was constructed using a limited portion of the field survey data, the low end of the USGS gage data (700 cfs to 1000 cfs), and a 10 cfs-zero water surface elevation to bracket the bottom of the flow range. For flowrates greater than 18,000 cfs, FEMA flood study elevations for the 10- and 50-year flood return periods were utilized with the USGS gage data to produce a third polynomial fit curve for head water elevation versus crest flowrate from

18,000 cfs to approximately 97,000 cfs. All three fit curves resulted in R-squared values exceeding 98%, indicating that the curves accounted for 98% of the observed data. The USGS gage data was given in

NAVD 88 datum, and the FEMA flood data is given in NGVD 29. A datum conversion of -0.311 m (1.02 ft) was obtained from the National Oceanic and Atmospheric Administration (NOAA) for conversion between NAVD 88 and NGVD 29 in the area of the project. A graph of the headwater data and polynomial fit curves is shown in Figure 3-7.

Figure 3-7: Headwater elevation derivation

Polynomial fit curves were used in estimated power and energy modeling so that for any given dam crest discharge flow an impoundment water surface elevation could be estimated. This requires that the flow over the crest of the dam be defined as a function of impoundment inflow, aesthetic flow rates, fisheries flow rates, and turbine flow rates.

3.2.2 Tailwater Elevation

The tailwater elevation, unlike the headwater elevation, is dependent upon the inflow (spillway discharge plus turbine flowrate plus environmental flows) and downstream control effects. The measured head differential was subtracted from the headwater elevation curve to give a tailwater elevation curve based upon the project inflow rate. The estimated headwater elevation model discussed above was used along with the rough field measurements collected by Alden and the

County and FEMA data to model tailwater surface elevations. A second order polynomial equation was fitted to the data set to give an equation for tailwater elevation versus total project inflow.

Similar to the headwater model, this polynomial fit curve was used for the power and energy model so that for any given project inflow, a tailwater surface elevation could be estimated. A graph of the tailwater data and polynomial fit curve is shown in Figure 3-8.

Figure 3-8: Tailwater elevation derivation

3.2.3 Gross Head

The total gross head was estimated by subtracting the tailwater elevation from the headwater elevation at a given river flow. Figure 3-9 plots the head water and tailwater curves illustrating the elevation differential. Figure 3-10 shows additional headwater and tailwater data found in drawings provided by the County. The source of headwater and tailwater elevations in Figure 3-10 is unknown.

Figure 3-9: Gross head based on tape measurements taken in 2016

Figure 3-10: Head and tailwater curves from the “Contract Drawings for Construction of Fish Passage

Facilities at Norristown Dam - Sheet G9 Fishway Schematic” Gannett Fleming. Inc 2008.

A review of figures 3-7 through 3-10 indicates that the tailwater level of the Norristown Dam rises at a faster rate than the impoundment level as flow increases above 25,000 cfs. This may be due to the configuration of the river downstream of the dam. It also points out that there is a level of flow in the river above which there is not sufficient net head to generate electricity. The minimum net head that a turbine-generator can operate at is dependent upon the type of equipment. This is investigated in

Section 6.0.

3.2.4 Head Loss

Head losses are typically incurred by friction and when flow is contracting, expanding, or changing direction. Head loss is a function of water velocity and increases exponentially as the velocity increases.

All hydropower projects are unique, and the site-specific geometry will dictate the extent of head loss.

To minimize head losses, site geometry should include gentle sloping bends, gradual transitions, and large cross-sectional area to reduce velocity, which needs to be balanced with overall project economics.

The primary form of head loss at a well-designed hydroelectric power plant is typically intake trash rack debris losses. These can be greatly reduced in the power production modeling by assuming that an automated trash rake will be installed. Where applicable, it is anticipated that the site will have an automatic trash rake cleaning system that will be configured such that it can be remotely activated by pressure transducers measuring water level differential across the trash rack and debris build up.

Other losses will occur at other flow points in the system. These include the transition section from the trash racks to the turbine and from the turbine outlet through the end of the draft tube. The head loss will increase as the flow velocity increases and more units are operating at maximum flows. These losses depend upon the final flow passage design, but good design practice should limit head losses to no more than 10% of gross head. Since the Norristown development designs are in the conceptual phase, a maximum head loss at maximum turbine flow was assumed to be 10%. Since head loss is proportional to velocity and velocity is proportional to flow rate squared, head loss at flows less than 100% were modeled through the flow rate squared times a constant. The constant is set so that at full flow the head loss is equivalent to 10% of gross head for a particular design option.

3.2.5 Net Head

The net head was calculated by subtracting the sum of the estimated head losses from the gross available head. This is the value ultimately used in power and energy modeling.

3.3 Flow

3.3.1 Schuylkill River Flow

The available flow for hydropower generation is typically a function of the hydrologic characteristics of the drainage basin upstream of the hydroelectric project less any flows that cannot be passed through the turbine. A drainage basin is the area of land that contributes water to a river. The basin can be characterized based on its land use (level of development), soil type, and the slope of the terrain, among other factors. The USGS StreamStats program was used to estimate the contributing drainage basin at the Norristown Dam as 1,760 square miles. The basin delineation is shown in Figure 3-11.

Figure 3-11: Norristown Dam drainage area (area in yellow) (StreamStats 2017)

The Schuylkill River is one of the largest tributaries of the Delaware River and is entirely located within the

State of Pennsylvania. The river's total drainage area is approximately 2,000 square miles. The eastern branch of the river originates around Tuscarora Lake about a mile east of the Village of Tuscarora and about a mile west of Tamaqua, at Tuscarora Springs in Schuylkill County. The west branch of the river starts near Minersville and joins the eastern branch at the Town of Schuylkill Haven. It then joins with the

Little Schuylkill River downstream in the Town of Port Clinton. Other major tributaries of the Schuylkill include Maiden Creek, Manatawny Creek, French Creek, and Perkiomen Creek. The Schuylkill joins the

Delaware River at the site of the Philadelphia Navy Yard (Wiki 2017b).

Typically at least a 20-year period of flow data is necessary to provide a representative average and range of flows and, hence, generation. The period of record of 2002 through 2021 was selected for power production modeling since the data from the USGS stream gauge was complete with continuous data points over that period. And, since this period of record is the time period immediately preceding the present, it is more similar to conditions in the watershed than periods earlier in time and should produce a more reliable estimate of flows in the future.

The USGS gauge utilizes the dam crest as a flow measuring weir therefore the USGS flow data can be directly used as the estimated available river flow for power production. Figure 3-12 and Figure 3-13 illustrate the available water resource at the Norristown Dam as summarized from USGS gage data and depict seasonal and yearly variations in river flow that may be expected at Norristown.

Figure 3-12: Average monthly flowrate

Figure 3-13: Yearly minimum, average, and maximum flow

A flow duration curve represents the relationship between the magnitude and duration of stream flows.

Duration in this context refers to the overall percentage of time that a particular flow is exceeded. A general flow duration cure was developed for the Norristown Dam site based on the USGS gauge average daily flowrate and is shown in Figure 3-14; monthly flow duration curves may be seen in

Appendix A.

Figure 3-14: Norristown dam flow duration curve

The 2016 FEMA Flood Insurance Study for Montgomery County, Pennsylvania included flood flow estimates, summarized in Table 3-2.

Table 3-2: Summary of flood flows

Discharge Flow (cfs)

10-year flood 62,900

50-year flood 93,700

100-year flood 109,000

500-year flood 146,000

3.3.2 Non-power Flow Requirements

It is anticipated that the project will be operated as a run-of-river facility with total outflows matching total inflows and the head pond maintained within a narrow elevation range, except when inflow exceeds the total turbine capacity, plus aesthetic flows and environmental flow. Aesthetic flow is water spilled over the dam spillway to maintain the existing look of the site. Since the original dam is a timber crib structure, keeping the timbers saturated by continuous flow over the concrete which covers the timber cribbing will reduce deterioration from repeated wetting and drying cycles. Environmental flows are those required to operate the fish ladder and maintain support the existing aquatic environment in the area immediately downstream of the dam.

Fisheries flows are the volume of water discharged through upstream and downstream fish passage facilities. The aesthetic and fisheries minimum flowrates cannot be used for power generation. Certain minimum flowrates may need to be discharged for aesthetic and fisheries purposes; this is discussed in detail in Section 7.2.

4.0 Review of New Technology

Alden investigated new and modified technologies for constructing hydropower projects and generating electricity to optimize the annual energy production and reduce costs to improve the project's economics. This investigation included evaluating new turbine designs and performance as well as civil structure design and arrangements.

4.1 AMJet ATS Turbine

The AMJet ATS-32 combines the turbine and generator into one unit (Figure 4-1). These units are suitable for sites with net head from 7 to 50 ft and flows from 98 to 250 cfs. The unit can be suspended in a conduit and does not require a powerhouse. According to the manufacturer, installation can be conducted within a few months and any repairs or replacements can be done within a day. The manufacturer has conducted bench test installations, however, as of the submittal of this report, there are no permanent installations that we are aware of.

Figure 4-1: AMJet ATS turbine (amjethydro.com)

4.2 Natel Energy Restoration Hydro Turbine (RHT)

The RHT is a high-performance compact propeller turbine (Figure 4-2). The unit is designed to be fish-friendly due to the uniquely designed thick blades; therefore, it reduces or removes the need for separate fish exclusion or other protection measures. These turbines are rated for 6.5 to 66 ft of head and generating capacities range from 30kW to 3MW. The compact unit allows for reduced installation costs and increased efficiency and flexibility. To date, there are two installations: Monroe Hydropower

Project in Oregon (300 kw), and Freedom Falls, Maine (50 kw). Natel is also in the process of scaling up their turbine.

Figure 4-2: Natel RTK (natelenergy.com)

4.3 KW River

This technology utilizes multiple Williams cross-flow turbine units to capture power from water over the weir of a low-head dam (). These units are designed to produce between 30 and 350kW of power. This technology is still in the initial stages of research and development and has only been tested in the laboratory.

Figure 4-3: Schematic of Williams crossflow turbine (kwriver.com)

4.4 VLH (Very Low Head) Turbine

The VLH is a Kaplan style turbine, which is capable of operating in very low heads from 5 to 15 ft. The unit has a self-supporting structure that can be stopped by closing the eight adjustable blades (Figure 4-4).

These units can operate in flows from 353 to 953 cfs and power output from 100 to 500 kW. Most of these units have been installed in Europe, however there is one installation in Canada.

Figure 4-4: VLH turbine (vlh-turbine.com)

4.5 Littoral Power Systems FlexStream

The FlexStream unit is based on a traditional crossflow design with an optimized guide vane and blade geometry, see Figure 4-5. The unit has an ogee contoured pressure casing that enhances both energy capture and energy recovery going through the draft tube. These units are designed for flows between

5 and 100 cfs and a head ranging from 9 to 100 ft. There has been one installation of a 35 kW FlexStream at Ward Hydro in Utah.

Figure 4-5: Littoral Power FlexStream turbine (littoralpower.com)

5.0 Request For Quotation of Turbine-Generator Equipment

To develop alternatives for the proposed new hydropower facility at the Norristown Dam, Alden solicited budgetary quotes from recognized hydroelectric equipment suppliers. The Request for

Quotation (RFQ) was sent to 15…